1. Field of the Invention
The present invention generally relates to an electrophotographic image forming apparatus, in particular, to an image forming apparatus and an image forming system in which a cartridge, that is, a process cartridge or a developing apparatus in the form of a cartridge (also referred to as a xe2x80x9cdeveloping cartridgexe2x80x9d) can be attached to the main body of the image forming apparatus and which are equipped with a residual developer amount detecting means for detecting a residual developer amount by using a storage means mounted in the cartridge.
Examples of the image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, an LED printer and a laser beam printer), an electrophotographic facsimile apparatus, and an electrophotographic word processor.
The cartridge detachably attachable to the image forming apparatus main body has at least one of an electrophotographic photosensitive body, a charging means for charging the electrophotographic photosensitive body, a developing means for supplying developer to the electrophotographic photosensitive body, and a cleaning means for cleaning the electrophotographic photosensitive body.
In particular, the process cartridge is obtained by forming at least one of a charging means, a developing means, and a cleaning means, and an electrophotographic photosensitive body into an integral cartridge, which is detachably attachable to the image forming apparatus main body. Alternatively, it is obtained by forming at least a developing means and an electrophotographic photosensitive body into an integral cartridge, which is detachably attachable to the image forming apparatus main body.
2. Description of Related Art
In an image forming apparatus, such as a copying machine or a laser beam printer, a beam corresponding to image information is applied to an electrophotographic photosensitive body (hereinafter referred to as the xe2x80x9cphotosensitive bodyxe2x80x9d) to form an electrostatic latent image, and a developer (toner) serving as the recording material is supplied to this electrostatic latent image by a developing means to thereby visualize the image. Further, the image is transferred from the photosensitive body to a recording paper sheet serving as the recording medium to thereby form an image on the recording paper sheet. The developing means is connected to a toner container serving as the developer containing part containing toner, and the toner is consumed as images are formed. In many cases, the developer containing part, the developing means, the photosensitive body, the charging means, etc. are formed into an integral process cartridge. When the toner has been used up, the user replaces the process cartridge with a new one, whereby it is possible to perform image formation anew.
Nowadays, in more and more cases the process cartridge or the image forming apparatus main body is equipped with a xe2x80x9cresidual toner amount level detecting meansxe2x80x9d (sequential residual developer amount detecting means) making it possible to know at any time the amount of toner for image formation remaining in the process cartridge.
In an example of the sequential residual developer amount detecting means, a metal plate is used. In this system, there is provided at least one flat sheet metal (metal plate) opposed to a developing roller serving as the developing means, and the developing roller and the metal plate or the metal plates or both of them are used as capacitor electrodes, utilizing the phenomenon in which the electrostatic capacitance between the electrodes changes with the amount of toner, which is an insulator. That is, if the inter-capacitor space formed by the metal plates and the developing roller is filled with toner, the electrostatic capacitance is large. As the toner is consumed, the amount of air in the space increases, thereby reducing the electrostatic capacitance.
Further, there is prepared a correcting table in which a relationship is previously established between the electrostatic capacitance between the metal plate and the developing roller and the toner amount, so that the residual toner amount level in the toner container can be calculated through measurement of the inter-capacitor capacitance.
In another system, a storage means (memory) which allows reading and writing is provided for each process cartridge (hereinafter referred to as the xe2x80x9ccartridgexe2x80x9d), and correction information, such as information on the inherent production tolerance of the cartridges, information on the present residual toner amount, etc. are stored, whereby the computation of the residual toner amount level using the above-mentioned xe2x80x9cresidual toner level detecting meansxe2x80x9d is performed more accurately.
However, when detection is performed by using such residual developer amount detecting means or storage means, it can occur that a detection value corresponding to an unstable toner state (for example, an unpredictable toner height), which exists in a range that can be detected by the residual developer amount detecting means, is stored. In that case, it is highly possible that the residual amount detection accuracy deteriorates.
The toner state may become unstable, for example, when the interval between the completion of printing operation for one job and the start of the next job (printing rest period) is very long.
In such cases, the state of the toner in the cartridge is unstable, and when the value at this time is used as the correction value, the accuracy of the residual toner amount detection value thereafter is always low, and it is quite possible that, even when it is not used as the correction value, a detection value of low accuracy will be temporarily obtained.
The present invention has been made in view of the above, and an object of the present invention to provide an image forming apparatus and an image forming system in which if the toner is put in an unstable state as a result of a long printing rest period, the detection accuracy does not deteriorate.
In order to attain the above-mentioned object, according to the present invention, there is provided an image forming apparatus to which a cartridge is detachably attachable, the cartridge having: a developing apparatus equipped with a developer containing portion containing a developer, a residual developer amount detecting means for detecting a residual developer amount in the developer containing portion, and a storage means capable of storing the latest residual developer amount information, wherein
the image forming apparatus includes:
a continuous rest time counter for counting a continuous rest time of a driving system of the image forming apparatus; and
a control means for prohibiting updating of the residual developer amount information to the storage means for a predetermined interval when the continuous rest time counter indicates a time not shorter than (equal to or more than) a predetermined time.
Further, according to the present invention, there is provided an image forming system for forming an image on a recording medium by using a cartridge detachably attachable to an image forming apparatus,
the image forming system comprising:
(a) a cartridge having: a developing apparatus equipped with a developer containing portion containing a developer; a residual developer amount detecting means for detecting a residual developer amount in the developer containing portion; and a storage means capable of storing the latest residual developer amount information; and
(b) an image forming apparatus main body equipped with a continuous rest time counter for counting a continuous rest time of a driving system, and a control means which prohibits updating of the residual developer amount information to the storage means for a predetermined interval when the continuous rest time counter indicates a time not shorter than a predetermined time.
Preferably, the predetermined interval is a predetermined driving time of the driving system of the image forming apparatus. Alternatively, the predetermined interval corresponds to a predetermined number of printed sheets.
Preferably, the residual developer amount detecting means outputs a signal obtained by measuring an electrostatic capacitance between at least two electrodes.
Preferably, an image forming system according to the present invention further comprises an indication means, in which a signal for indicating information on a detected residual developer amount is transmitted to the indication means for display.
Preferably, an image forming system according to the present invention is further capable of communicating with an apparatus having an indication means, in which a signal for indicating information on a detected residual developer amount is transmitted to the apparatus having the indication means for display.
Preferably, the cartridge further includes at least one of an electrophotographic photosensitive body, a charging means for charging the electrophotographic photosensitive body, a developing means for supplying developer to the electrophotographic photosensitive body, and a cleaning means for cleaning the electrophotographic photosensitive body.
In accordance with the present invention, the detection value immediately after a long-term rest, when the developer is in an unstable state, is not stored, so that if the developer is put in an unstable state as a result of a long printing rest period, there is no deterioration in detection accuracy, and it is always possible to perform detection in a stable manner without deteriorating the residual developer amount detection accuracy, thus making it possible to achieve a stable image quality.
These and other objects and advantages of the invention may be readily ascertained by referring to the following description and accompanying drawings.